First Non-Repeating Character

Given a string s, return the index of the first character that appears exactly once. If no such character exists, return -1.

Inputs = "leetcode"Output0Why`'l'` appears once and is the first unique character.

Inputs = "loveleetcode"Output2Why`'v'` is the first character with frequency 1.

Inputs = "aabb"Output-1WhyNo character appears exactly once.

Problem

Given a string s, return the index of the first character that appears exactly once. If no such character exists, return -1.

Examples

Example 1

Inputs = "leetcode"Output0Why`'l'` appears once and is the first unique character.

Example 2

Inputs = "loveleetcode"Output2Why`'v'` is the first character with frequency 1.

Example 3

Inputs = "aabb"Output-1WhyNo character appears exactly once.

Constraints

`1 <= len(s) <= 10^5`
`s` consists of English lowercase letters
Return `-1` if no non-repeating character exists

Problem

Given a string s, return the index of the first character that appears exactly once. If no such character exists, return -1.

Examples

Example 1

Inputs = "leetcode"Output0Why`'l'` appears once and is the first unique character.

Example 2

Inputs = "loveleetcode"Output2Why`'v'` is the first character with frequency 1.

Example 3

Inputs = "aabb"Output-1WhyNo character appears exactly once.

Constraints

`1 <= len(s) <= 10^5`
`s` consists of English lowercase letters
Return `-1` if no non-repeating character exists

Problem

Given a string s, return the index of the first character that appears exactly once. If no such character exists, return -1.

Examples

Example 1

Inputs = "leetcode"Output0Why`'l'` appears once and is the first unique character.

Example 2

Inputs = "loveleetcode"Output2Why`'v'` is the first character with frequency 1.

Example 3

Inputs = "aabb"Output-1WhyNo character appears exactly once.

Constraints

`1 <= len(s) <= 10^5`
`s` consists of English lowercase letters
Return `-1` if no non-repeating character exists

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First Non-Repeating Character

Problem

Examples

Constraints

Problem

Examples

Constraints